A fluid-assisted fused deposition modeling (FA-FDM) 3D printing technique was proposed and employed to create anisotropically thermally conductive polymer composites (aniso-TCPCs). These composites have precisely controllable heat conduction pathways achieved by spraying boron nitride (BN) on both sides of the FDM 3D printed POE/PP materials. At the same BN content (c_BN), the thermal conductivity (λ) of the aniso-TCPCs is higher than that of the isotropic composites. When c_BN = 60 wt%, the λ of the aniso-TCPCs could reach 1.43 W m⁻¹ K⁻¹, improved over 510 % as compared to the POE/PP matrix. Both experimental and simulation results show that the design of the anisotropically thermally conductive pathways can significantly improve the thermal conductivity of the polymer composites for efficient heat dispersion. Overall, the present study would provide a point of reference for the rational design of effective heat dissipation materials with highly and precisely tunable heat transfer pathways.